The mechanisms of synaptic tramsmission in the vertebrate retina and its role in visual information processing will be studied by intracellular recording from single neurons in the amphibian retina. The effects of various suspected neurotransmitter substances and specific antagonists on the resting potential, input resistance and light responses of different types of retinal neurons will be examined. The test substances will be applied to the retina in known concentrations by a superfusion system which allows changes to be made in the bathing medium while continuosly recording from a single neuron. Particular questions to be studied are the interaction of excitatory and inhibitory inputs in ganglion cells, the synaptic connections which mediate center-surround antagonism in the inner and outer synaptic layers of the retina, the generation of transient responses in amacrine and ganglion cells, and the types of receptors at which rod cone neurotransmitter substances act on second-order cells in the retina. The immediate aim is to obtain information on the different synpatic inputs to each type of retinal neuron, the transmitter substances which mediate these inputs, and the sources of the inputs. The long-term goal of this research is to develop a more complete model of how different neurons interact to process visual information.